Anesthesia devices with an inspiratory branch and an expiratory branch are shown in the state of the art. So-called half-closed anesthesia systems are used for reusing the portion of anesthesia gas in the expired gas. Such a half-closed anesthesia system is shown in U.S. Pat. No. 5,520,172 A. So-called fully closed respiration systems are used in order to further reduce the amount of anesthesia that must be conveyed unused into the half-closed anesthesia circulation. Besides the closed circuit, an array of valves are used for feeding fresh gas and inhalants into the breathing circuit and controlled such that the loss of anesthesia gas is as low as possible.
DE 10 2006 032 498 B3 shows a respiration or anesthesia and therapy device for patients which has a controllable valve in the expiration branch to keep the loss of anesthesia gas as low as possible.
A respirator with a breathing circuit is described in DE 199 58 532 C1. In this breathing circuit, defined breathing gas volumes are fed to the patient and the current operating state is reliably monitored. A rotary compressor as a gas-feeding element, a reversible breathing gas reservoir, gas volume flow sensors, nonreturn valves, a controllable stop valve and an associated measuring and regulating unit are present as elements in the respirator.
DE 197 14 644 C2 shows a gas feeding means for a respiration and anesthesia device. The gas feeding means for a respiration and anesthesia device is designed in the form of a radial compressor with backwards curved blades. A compressor wheel, which feeds a quantity of air from a gas inlet to a gas outlet, is arranged rotatably in a fixed housing. The compressor wheel is driven via an electric motor.
A closed respiration system, which has, starting from a patient connection or from a Y-piece, an inspiratory branch and an expiratory branch, which are in turn connected to one another via a rebreathing line within the system, so that gas expired by the patient can be returned to the inspiratory branch, while it flows, among other things, through a CO2 absorber and gas components absorbed by the patient are replaced by means of a fresh gas supply unit, is already known from the instructions for use of the respiration system of the “Zeus Infinity Empowered” respiration system of Dräger Medical GmbH.
It is necessary in such closed respiration systems for the entire breathing circuit comprising the inspiratory branch, expiratory branch and rebreathing line, to be able to be flushed with oxygen as quickly as possible in order to abruptly increase the oxygen concentration in the breathing gas, which is fed to the patient.
This is achieved in the system described in the instructions for use mentioned in the introduction by maintaining, on the one hand, a constant breathing gas flow in the respiration system of the anesthesia apparatus and in the entire breathing circuit up to the Y-piece leading to the patient by means of the respiration drive designed as a radial compressor and, on the other hand, by being able to admit oxygen into the breathing circuit by means of an oxygen flushing means arranged between the expiratory branch and the CO2 absorber.
Such an oxygen flushing means is known as an “O2 flush” and is intended typically for anesthesia apparatuses as an operational control accessible to the user in this form. The oxygen flushing means has an oxygen port for this, for example, as a port to an oxygen tank that is under pressure or to a pressurized oxygen line.
Furthermore, a means is present, with which an oxygen volume flow can be set and dispensed when actuating the flushing means. Based on the constant flow, the oxygen that may be optionally admitted is then distributed in the entire breathing circuit.
However, such a system is associated with the drawback that a gas flow must be continuously maintained in the breathing circuit in order to ensure that the oxygen is also distributed in the entire breathing circuit, and it does not happen that parts thereof are not flushed. If the latter happened, a so-called rebound effect could occur, during which breathing gas with a low oxygen concentration is again fed after a short time, during which breathing gas with high oxygen concentration was admitted to the patient after actuation of the oxygen flushing means.
Another problem in closed respiration systems is that it is desirable, on the one hand, to provide a constant fresh gas flow from the fresh gas supply unit, which flow is now flowing through an anesthetic evaporator, so that this constant flow can be used in the evaporator to absorb the anesthetic.
The general mode of operation of an anesthetic evaporator is known from GB 1 503 261.
Such an evaporator cannot be operated reliably if the intensity of the flow varies as a result and if a pulsed flow is used. However, the advantage of anesthetic evaporators is that these make do without complicated electrical components and operate very reliably if flow passing through them is continuous.
However, an electric injection pump, which injects anesthetic into the pulsed fresh gas flow, is used instead of an anesthetic evaporator in the respiration system explained above, which is described in the instructions for use. This complicates the system described further.